existing the most interesting instances in which this great faculty is alternately the victim and the tyrant of the sense of sight.
Amongst many works on this subject we may cite that of Brière de Boismont on "Hallucinations, Apparitions, Visions, &c.," from which we shall draw largely in the following pages. The examples we shall give will be those only in which the victims of the hallucination were in the full enjoyment of their mental faculties, and could healthily analyze the sensations and impressions to which they were subjected.
One of the first of these bears upon those diseases of the eye to which allusion was made in Chapter IV. Towards the end of 1833, a poor washerwoman who was tormented grievously with rheumatic pains gave up her business, and took to sewing for her livelihood. Being but little accustomed to this kind of work, she was compelled to sit over her needle late at night in order to save herself from starving. The unwonted strain upon the eyes soon brought on ophthalmia, which speedily became chronic. Nevertheless, she continued her work, and fell a prey to diplopia, or double sight in each eye. Instead of a single needle and thread, she saw four continually at work, everything else about her being similarly multiplied. At first she took no notice of the singular illusion, but at last both imagination and sight joined arms against the judgment, and the poor creature imagined that Providence had taken pity on her forlorn condition, and had worked a miracle in her favour by bestowing on her four pair of hands in order that she might do four times her usual amount of work.
The following is another instance of the passage of illusion into hallucination. A man fifty-two years old, of a plethoric constitution, after having suffered from a defect in his visual functions that caused him to see ob-
